My webcam was working fine but now on programs such as Skype and Facebook it does not work. There is no error, but it doesn't find the webcam.
Any help would be much appreciated
The main problem could be that the driver files may have been altered when you installed something else, the best bet is to just re-install the webcam drivers or do a system restore to when you last remember using your webcam. But the system restore could be used as a last resort.
I would tend to agree with Sandeep. Try reinstalling the webcam drivers and this should fix any issues you are having (as the drivers are what tells the computer "this thing is a webcam, this is how you use it" and with bad drivers your computer won't recognise your webcam (as you were explaining in your problem). You can either google your model number plus "driver" or if any disk came with your webcam then try putting that in as it may contain drivers.
Also as Sandeep said - if you really must then use System Restore a last resort to try and restore registry (and driver?) settings.
[Sidenote: Try and be more specific if at all possible in all questions you ask online as it's difficult to solve problems such as this without specifics]